JPS5813592B2 - Polyester materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermosetting polyester resin composition, and more specifically, it contains terephthalic acid, p-oxybenzoic acid, and saturated aliphatic dicarboxylic acid as the main acid components, and ethylene glycol as the main alcohol component. The present invention relates to a novel polyester resin composition suitable as a binder resin for powder coatings, which comprises a polyester polymer, a block aliphatic polyisocyanate, and a hexamethylol melamine derivative.

Powder paints were introduced as a solution to the disadvantages of solvent paints, which emit expensive organic solvents into the atmosphere, but recently they have attracted attention as non-polluting paints.

Furthermore, it has shown rapid growth in recent years because it has many advantages such as not requiring multiple layers of painting, the paint can be recovered and reused, and a high coating yield can be obtained.

Normally, in order to use a resin as a binder for powder coatings, it must: (1) be easily pulverized into micro powder;

(2) Do not block during transportation or storage.

(3) It flows at a relatively low temperature and pigmentation is easy.

(4) Scales that form a strong and beautiful coating film by baking at low temperatures and for a short time.

(5) The coating film has excellent properties such as weather resistance, solvent resistance, moisture resistance, stain resistance, and adhesion to metals.

It is desirable to meet the following requirements.

As a result of intensive research to develop a binder resin for powder coatings that satisfies these requirements, the present inventors found that: - maintaining the excellent properties of polyethylene terephthalate and polyethylene oxybenzoate, and combining the terephthalic acid component with p- Special effects due to copolymerization with oxybenzoic acid component, namely: (1) Excellent crushability is imparted.

(2) Flows at a relatively low temperature for easy pigmentation.

(3) Forms a beautiful enamel coating.

(4) Improve adhesion to metals, especially iron.

(5) No locking property despite lowering the liquefaction temperature.

As a binder resin for powder coatings that takes advantage of It was discovered that a composition consisting of the following had favorable properties, and a separate proposal was made.

However, in thermosetting resin compositions that use a large amount of blocked isocyanate, the blocking agent released during curing generally scatters, so if harmful substances such as phenol, pyrocatechol, mercabutan, etc. are used as the blocking agent, they can be recovered. equipment is required.

In addition, many of the commonly used inexpensive incyanates, such as tolylene diisocyanate and diphenylmethane diisocyanate, have an incyanate group directly bonded to the aromatic nucleus, and the polyester resin composition obtained from these inocyanates cannot be left exposed to the atmosphere. There is a risk of yellowing, so a delicate formulation is required.

Progress is being made in the development of non-yellowing isocyanates with improved weather resistance, but they are generally expensive.

In addition, the present inventors have found that a resin composition comprising the above polyester polymer and a hexamethylolmelamine derivative has excellent properties as a binder resin for powder coatings, and has separately proposed the same.

However, although this method can also produce a beautiful and strong paint film, the hardened paint film obtained by applying a thick coating with a film thickness of 200μ or more has the drawback that wrinkles and foaming are noticeable and the beauty is lacking. are doing.

The inventors of the present invention sought to develop an ideal material as a binder resin for powder coatings.As a result of further studies, they achieved this objective very effectively as described below.

That is, terephthalic acid component 40 to 80 mol%, p-oxybenzoic acid component 20 to 60 mol%, and saturated aliphatic dicarboxylic acid component 0 to the total acid components forming the polyester.
A polyester polymer with an average degree of polymerization of 5 to 50 and an acid value of 15 or less, with ethylene glycol as the main acid component and ethylene glycol as the main alcohol component, and 0.1 to 1. A polyester resin composition consisting of 5 equivalents of block aliphatic polyisocyanate and 0.1 to 2.0 equivalents of a hexamethylolmelamine derivative having the following structural formula has satisfactory properties as a binder resin for powder coatings. It was equipped with the following.

(In the formula, R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

) The polyester resin composition of the present invention can not only be produced at a low cost, but also has superior properties compared to amino resins or urethane resins, and can be used to cure hexamethylolmelamine derivatives and block aliphatic polyisocyanates, which have different reaction rates. By using it as an agent, the curing reaction is controlled and a coated surface with excellent coating film smoothness can be obtained, and the excellent properties of both amine resins and urethane resins are produced.

The polyester polymer used in the present invention has an acid value within a preferable range because the acid acts as a crosslinking reaction catalyst between the polyester polymer and the hexamethylolmelamine derivative.
That is, it must be adjusted to 15 or less, and the average degree of polymerization must also be adjusted within the range of 5 to 50 to ensure sufficient fluidization during baking.

Saturated aliphatic dicarboxylic acids that can be used as acid components include dicarboxylic acids having 4 to 14 carbon atoms such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dotecane dicarboxylic acid, and alcohol components include ethylene glycol, There are neopentyl glycol and the like, but it is necessary that at least 40 mol% or more of it be ethylene glycol.

The polyester polymer used for producing the polyester resin composition of the present invention has a terephthalic acid component of 40 to 80 mol% and a p-oxybenzoic acid component of 20 to 60 mol% based on the total acid components.
It consists of a polymer having an average degree of polymerization of 5 to 50 and an acid value of 15 or less, with 0 to 30 mol% of a saturated aliphatic dicarboxylic acid component as the main acid component and ethylene glycol as the main alcohol component.

Furthermore, terephthalic acid component 40 to 80 mol%, p-oxybenzoic acid component 20 to 60 mol%, and saturated aliphatic dicarboxylic acid component 0 to 80 mol%, based on the total acid components forming the polyester.
30 mol% as the main acid component, ethylene glycol as the main alcohol component, and an amount of trivalent acid that does not gel according to the average degree of polymerization within a total amount of acid component and/or alcohol component of 30 mol% or less. Polyester polymers used in the present invention also include copolymerized polyhydric carboxylic acids and/or trihydric or higher polyhydric alcohols having an average degree of polymerization of 5 to 50 and an acid value of 15 or less.

Trivalent or higher polyvalent carboxylic acids include trimellitic acid and pyromellitic acid, and trivalent or higher polyvalent alcohols include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, cypentaerythritol, mannitol, etc. There is.

The block aliphatic polyisocyanate used in the present invention refers to the aliphatic polyisocyanate and the isocyanate group of the aliphatic polyisocyanate.
．． This is obtained from 0 equivalents of blocking agent.

The aliphatic polyisocyanates referred to herein are all polyisocyanates in which the incyanate group is not directly bonded to an aromatic nucleus, and the yellowing of the cured coating film K is less likely to occur.

Such aliphatic polyisocyanates include inphorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.
- Trimethylhexamethylene diisocyanate, xylylene diisocyanate, etc., and polymers of these incyanates and adducts obtained by reacting these incyanates with active hydrogen compounds such as ethylene glycol, trimethylolpropane, and pentaerythritol. Also included.

As the blocking agent, active hydrogen compounds such as ε-caglolactam, acetone oxime, methyl ethyl ketone oxime, ethyl malonate, phenol, acetylacetone, ethyl a7toacetate, and pyrrolidone can be used.

The hexamethylolmelamine derivative used in the present invention has the following structure, and includes hexamethoxymethylmelamine, hexabutoxymethylmelamine, and the like.

(In the formula, R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

) The polyester resin composition of the present invention is prepared by transesterifying dimethyl terephthalate and methyl p-oxybenzoate with ethylene glycol and, if necessary, neopentyl glycol, and, if necessary, transesterifying the polyester resin composition with a saturated aliphatic dicarboxylic acid. Furthermore, after an esterification reaction by adding a trivalent or higher polyhydric carboxylic acid or/and a trivalent or higher polyhydric alcohol, a polyester polymer having a desired degree of polymerization is prepared by polycondensation under reduced pressure. It is prepared by melt-mixing a block aliphatic polyisocyanate and a hexamethylol melamine derivative in an amount of 01 to 1.5 equivalents to the hydroxyl groups of the polyester polymer at a temperature of 130° C. or lower.

Note that the polyester polymer in the present invention is not limited to monomer-based starting materials; for example, polyethylene terephthalate, polyethylene oxybenzoate, or copolyesters mainly composed of these are used in combination with ethylene glycol and/or neopentyl glycol, etc. It can also be effectively applied when regenerating by depolymerizing with polyhydric alcohol.

Next, the present invention will be specifically explained by showing Examples and Comparative Examples.

Examples 1 to 10 Dimethyl terephthalate (hereinafter abbreviated as DMT), methyl p-oxybenzoate (hereinafter abbreviated as OEBM) and ethylene glycol (hereinafter abbreviated as EG) in the amounts shown in Table 1 and zinc acetate as a catalyst. A transesterification reaction was carried out using 01 mol of neopentyl glycol (hereinafter referred to as NPC).
adipic acid (hereinafter abbreviated as ADA), azelaic acid (hereinafter abbreviated as AZA), sebacic acid (hereinafter abbreviated as SEA)
), trimellitic acid (hereinafter abbreviated as TMA), trimethylolfuropane (hereinafter abbreviated as TP), and pentaerythritol (hereinafter abbreviated as PE),
If necessary, an esterification reaction is performed, followed by polycondensation at a reduced pressure of 1■Hg and a reaction temperature of 200 to 240°C to obtain the results shown in Table 2.
Average degree of polymerization 9.5 to 35.0, liquefaction temperature 75 as shown in
~80°C polyester polymer was synthesized.

Subsequently, 50 moles of inphorone diisocyanate and 100 moles of ε-cabrolactam were reacted at 80° C. in a nitrogen atmosphere to prepare a blocked isocyanate (designated as block isocyanate ①).

Blocked isocyanate was prepared by reacting 50 moles of 2,2,4-trimethylhexamethylene diisocyanate and 100 moles of ε-caglolactam at 80° C. in a nitrogen atmosphere (referred to as Blocked Isocyanate ①).

Blocked isocyanate was prepared by reacting 50-El of xylylene diisocyanate and 100 moles of methyl ethyl ketone oxime at 80° C. in a nitrogen atmosphere (referred to as block isocyanate ①).

The block isocyanate and hexamethylol melamine derivative shown in Table 3 were added to the polyester polymer shown in Table 2 for 1 hour.
The polyester resin compositions shown in Table 4 were prepared by melt-mixing at 20°C.

However, OH: hydroxyl equivalent of polyester polymer N
CO: Isocyanate group equivalent OR: Methoxy group or butoxy group equivalent A coating composition obtained by melt-mixing 100 parts by weight of the above polyester resin composition, 40 parts by weight of rutile titanium oxide, and 2 parts of a surface conditioner in a roll mill is micronized. Victory Mill VP-
When crushed using a Type 1 crusher (manufactured by Hosokawa Iron Works), it was possible to feed more than 35 kg/hr.
It was possible to prepare a fine powder in which more than 95% of the powder passed through a 150 mesh sieve.

Using the part of the prepared powder that passed through 150 mesh,
．． Electrostatic coating was applied to a 8x100x200 (Oni) steel plate using a Seiden powder coating machine 720 model (manufactured by GEMA) to a film thickness of 200 microns, and after baking at 180°C for 30 minutes, a beautiful enamel coating was obtained. were obtained, the following tests were conducted and the results shown in Table 5 were obtained.

) Impact resistance test; DuPont type (1/2"-1kg)
.

(2) Erichsen test; according to JIS Z-2247.

(3) 60° specular reflection; conforms to JIS Z-874 1.

(4) Heat resistance test; according to JIS K-6902.

(5) Boiling resistance test: Erichsen test is conducted after processing according to JISK-6902.

(6) Stain resistance test: According to JIS K-6902.

(7) Acetone resistance test; according to JISK-6911.

(8) 60° specular reflectance after 100 hours of due cycle weather meter processing.

(9) Weight loss rate due to baking.

It should be noted that none of the powders developed blocking even when left at 40°C for 7 days.

Reference Example I DMT 56 mol, OEBM 44 mol, EG 136 mol, TPO. A polyester polymer having a liquefaction temperature of 120°C and an average degree of polymerization of 95 was prepared in the same manner as in the example using 5 mol, but the polymer was tough and could not be pulverized to the extent that it could pass through a 100 mesh sieve. .

Reference Example 2 A polyester polymer having a liquefaction temperature of 40° C. and an average degree of polymerization of 4.0 was prepared in the same manner as in Example 2, but the polymer had significant blocking properties at room temperature and could not be pulverized by pulverization. Ta.

Reference Example 3 Same as Example 1, but using ADA instead of OEBM.
A polyester polymer having a liquefaction temperature of 55° C. and an average degree of polymerization of 9.2 was prepared using the same method, but the polymer had a significant blocking property at room temperature and could not be pulverized by pulverization.

Reference Example 4 Same as Example 1, but using DMT instead of OEBM.
was used to prepare a polyester polymer with an average degree of polymerization of 9.2, but the melting point of the polymer was 250°C, and block aliphatic polyisocyanate could not be melt-mixed at a temperature of 150°C or lower.

Reference Example 5 The baked coating film of a resin composition obtained by melt-mixing 15 moles of hexamethoxymethylmelamine in the same manner as in Example 1 had a lot of wrinkles and foaming, and was poor in smoothness. .

Reference Example 6 Baking coating of a resin composition obtained in the same manner as in Example 1, but using a blocked isocyanate obtained from aromatic tolylene diisocyanate and ε-cubic lactam instead of blocked isocyanate I. The membrane developed significant yellowing and chalking during 65 hours of Teu Cycle Weathermeter treatment.

In addition, the average degree of polymerization in Examples and Reference Examples refers to a paper pressure osmometer (manufactured by KNAUER).
It is obtained by converting the average molecular weight measured using the method according to the composition.

A comparison of Examples and Reference Examples reveals that the polyester resin composition of the present invention has particularly desirable properties as a binder for powder coatings.

This is a polyester polymer obtained by copolymerizing a terephthalic acid component and a p-oxybenzoic acid component and controlling the average degree of polymerization within a preferable range, and can be cured without damaging the properties of the polyester polymer. This is largely due to the combination of block aliphatic polyisocyanate and hexamethylolmelamine derivative.

Claims (1)

[Claims] 1. Terephthalic acid component 40 to 80 mol%, P-oxybenzoic acid component 2, based on the total acid components forming the polyester.
0-60 mol%, saturated aliphatic dicarboxylic acid component 0-30
Average degree of polymerization 5 to 50, acid value 15 with mol% as the main acid component and ethylene glycol as the main alcohol component
The following polyester polymer, a block aliphatic polyisocyanate of 0.1 to 1.5 times the equivalent of the hydroxyl group of the polyester polymer, and a hexane having the following structural formula of 0.1 to 2.0 times the equivalent of the hydroxyl group of the polyester polymer. A polyester resin composition for powder coatings comprising a methylolmelamine derivative. (In the formula, R represents hydrogen or an alkyl group having 1 to 4 carbon atoms.)